1. Field of the Invention
The present invention relates to lenses or lamp coverings for exterior vehicle lamps wherein the lens is molded from a high nitrile polymer comprising from 55 to 85 percent by weight of a nitrile monomer unit and from 15 to 45 percent by weight of a monovinylidene aromatic monomer.
2. Description of the Prior Art
Exterior lamps are widely used in land, sea and air vehicles. Examples of exterior vehicle lamps include the parking lights, tail lights, stop lights, backup lights, running lights, signal lights, etc., which are found in automobiles, boats and aircraft.
Exterior lighting fixtures on vehicles usually comprise a lamp, which is the term used for the light source and supporting structure, and a covering over the lamp which is referred to as a lens. The lens serves as a protective covering over the lamp and may additionally serve to focus or diffuse the light transmitted by the lamp and to transmit light of different colors, e.g., red, amber, green, white, etc. The lenses used for exterior lamps on vehicles must have good optical properties and impact resistance, high heat distortion, good weatherability, and be readily molded into many diverse and sometimes complex shapes.
For some time now polymethylmethacrylate (PMMA) has been widely used to prepare lenses for exterior lamps. However, a need exists in the art for exterior lenses which can be molded faster and which exhibit improved chemical resistance and improved weatherability. The present invention provides such lenses.